Affirmative Imperative forms of imperfective verbs are used (1) for impatient requests ("Why aren't you talking to me? Do talk to me") and (2) orders ("Talk to me. I order you"), whereas the perfective imperative forms are used for less emotional polite requests ("Will you please talk to me" = Поговори со мной, пожалуйста). Only imperfective verbs are used in negative requests ("Не говори(те) никому!" = "Don't tell anyone!"). The negative imperative of perfective verbs is synonymous with the if-clause of the unreal conditional: "Не поговори он (=Если бы он не поговорил) со мной вчера, я бы так и не узнал, что произошло" means "Should he not have talked / If he hadn't talked to me yesterday, I would have never learned what had happened". There are also a few cases where negative imperative forms of perfective verbs are used idiomatically, e.g. "Не скажи(те)!" means "It isn't necessarily the case!"/"I'd rather disagree with you". Other examples include biblical commendments (Не убей, Не укради, Не сотвори себе кумира), although in more modern translation of the Bible imperfective verbs are used instead.

We use the preposition со istead of с, when the following word starts with two consonants of which the first one is в, з, с, ж, ш, or м. Exеptions to this rule include phrases with the words враг =enemy (с врагом, с врагами), млекопитающее = mammal and Млечный Путь = Milky Way (с млекопитающими, с Млечного Пути).

You're right. It could also be used when your friend's or close relative's talk makes you feel better. There is song that was popular in Russia in 1970s which starts with the phrase "Поговори со мною, мама". Check it up on YouTube.